Predicting Stochastic Lightning Mechanical Damage Effects on Carbon Fiber Reinforced Polymer Matrix Composites

Three stochastic air blast models are developed with spatially varying elastic properties and failure strengths for predicting lightning mechanical damage to AS4/3506 carbon/epoxy composites subjected to \u3c 100 kA peak currents: (1) the conventional weapon effects program (CWP) model, (2) the coupled eulerianlagrangian (CEL) model, and (3) the smoothed-particle hydrodynamics (SPH) model. This work is an extension of our previous studies [1–4] that used deterministic air blast models for lightning mechanical damage prediction. Stochastic variations in composite material properties were generated using the Box-Muller transformation algorithm with the mean (i.e., room temperature experimental data) and their standard deviations (i.e., 10% of the mean herein as reference). The predicted dynamic responses and corresponding damage initiation prediction for composites under equivalent air blast loading were comparable for the deterministic and stochastic models. Overall, the domains with displacement, von-Mises stress, and damage initiation contours predicted in the stochastic models were somewhat sporadic and asymmetric along the fiber’s local orientation and varied intermittently. This suggests the significance of local property variations in lightning mechanical damage prediction. Thus, stochastic air blast models may provide a more accurate lightning mechanical damage approximation than traditional (deterministic) air blast models. All stochastic models proposed in this work demonstrated satisfactory accuracy compared to the baseline models, but required substantial computational time due to the random material model generation/assignment process, which needs to be optimized in future work

Estimating the Production Potential of Major Crops in Pakistan’s Irrigated Agriculture during the 21st Century

Land and irrigation are the basic resources in agriculture. The role and importance of these resources and their contribution towards productivity, in the context of the country’s increasing population, can hardly be exaggerated. Pakistani agriculture is set in a very distinctive situation of an increasing population on the one hand and diminishing resources on the other. The population of Pakistan was reported to be 131.63 million in 1996 and is projected to be 207 million in 2013 [Pakistan (1996) and WSIP (1990)]. The agriculture sector has to face the difficult task of doubling the existing food production by the turn of this century. The situation demands horizontal and vertical growth in the productivity, either by bringing more land under cultivation, or by increasing the cropping intensity of the existing land resources. This can also be accomplished by bringing more land under cultivation from the cultivable uncultivated area (a large proportion of which exists on medium and large farms under waterlogged or saline conditions). In this context, it becomes important to identify the nature of the relationship that exists between farm size and unculturable wastelands and the kinds of changes the green revolution/SCARPs projects introduced to this relationship.

Heterogeneous catalysis of some redox reactions by platinum

The heterogeneous catalysis by platinum of redox reactions in aqueous solution has been investigated. In Part I of the thesis the kinetics of the heterogeneous reactions of iodide with hexacyanoferrate(III), with aquo-iron(III) and with sulphato-iron(III) are examined with platinum as catalyst. The result for the Fe(CN)63-/I - reaction indicates that the catalytic rate is at least partly controlled by the rate of diffusion of Fe(CN)63- from the bulk solution up to the platinum surface. The state of the platinum surface is also shown to affect the observed reaction rate. It has been found that the heterogeneous reaction has a rate dependent upon [K+] and the results are consistent with an ion-pair, K+...Fe(CN) 3-/I-, being one species involved in exchanging electrons with the platinum surface. In the reaction of ferric ion with iodide the results indicate that Fe(OH)2+ is the species more suited to the heterogeneous process. In the FeSO4+/I- reaction it has been observed that the. heterogeneous rate is due to FeSO4 +. Both these latter heterogeneous reactions have an appreciable temperature co-efficient. The order of the heterogeneous component of reaction with respect to each reactant has always turned out to be one or less. In Part II the rate of the reaction between tris (dipyridyl)-iron(III) and iodide has been measured spectrophotometrically by observing the optical density at 520 nm where absorption is virtually due to the formation of tris(dipyridyl)iron(II). The effects of several variations in reaction conditions are studied. The main reaction is shown to be first order in Fe(dipy)33+ and first to second order in I-. Finally a possible reaction mechanism is proposed. This reaction is unaffected in rate by the presence of platinum surface. The effect of platinum on the reaction between cerium(IV) and thallium(I) in different acidic media such as HNO3, H2SO4 and HClO4 is also studied. It has been found that the reaction occurs almost exclusively via a heterogeneous catalysed path. Finally in the reaction of peroxodisulphate with oxalate ion in the presence of silver(I) as a catalyst, it has been found that the rate of the reaction in the presence of silver(I) ion is uncatalysed further by the presence of platinum. Some implications of these results are discussed.<p

A New Weighting Scheme in Weighted Markov Model for Predicting the Probability of Drought Episodes

Drought is a complex stochastic natural hazard caused by prolonged shortage of rainfall. Several environmental factors are involved in determining drought classes at the specific monitoring station. Therefore, efficient sequence processing techniques are required to explore and predict the periodic information about the various episodes of drought classes. In this study, we proposed a new weighting scheme to predict the probability of various drought classes under Weighted Markov Chain (WMC) model. We provide a standardized scheme of weights for ordinal sequences of drought classifications by normalizing squared weighted Cohen Kappa. Illustrations of the proposed scheme are given by including temporal ordinal data on drought classes determined by the standardized precipitation temperature index (SPTI). Experimental results show that the proposed weighting scheme for WMC model is sufficiently flexible to address actual changes in drought classifications by restructuring the transient behavior of a Markov chain. In summary, this paper proposes a new weighting scheme to improve the accuracy of the WMC, specifically in the field of hydrology

On the Differential Market Reaction to Dividend Announcement: Evidence from an Emerging Equity Market

The corporate finance literature for market reaction to dividend announcements reports mixed result

DETERMINANTS OF REAL EXCHANGE RATE MOVEMENTS IN SOUTH ASIAN COUNTRIES: AN EMPIRICAL EVIDENCE

This study investigates the determinants of real exchange ratemovements in South Asian Countries. The determinants which are examined in the study are fiscal, monetary and other (stock returns, real income and political stability). Panel data of 15 years from 1998 to 2012 has been used in the study, where four cross sections are included. Multicollinearity test, panel unit root tests, Kao’s cointegration test and FMOLS (fully modified ordinary least square) are applied in the study. All the variables are found stationary at first difference although Kao’s cointegration test results are not found favorable for co-integration. However, FMOLS results are in favor of co-integration. Some variables are proved to have opposite direction as expected although they are found consistent with some previous studies

Relationship among Hypovitaminosis D, Maternal Periodontal Disease, and Low Birth Weight

Objective: To determine if low birth weight is associated with hypovitaminosis D and periodontal disease among a sample of Pakistani women residing in district Jhelum, Punjab.STUDY Design: Cross-sectional study nested in a large community-based longitudinal study.PLACE AND DURATION OF STUDY: Tehsil Pind Dadan Khan, District Jhelum, Pakistan from August 2012 to October 2015.METHODOLOGY: Women during 12-16th week of pregnancy were selected. Dental examination was performed. Probing depth \u3e3 mm was labeled as periodontal disease, whereas serum level 2500 g) babies. Odds ratio was applied to measure the strength of association of low birth weight with maternal hypovitaminosis D and also for maternal periodontal disease.Results: There were 62 participants in the study. The mean age of mothers was 26.7 ±4.5 years. It was alarming to observe that 53 (85%) participants had vitamin D deficiency. However, periodontal disease was only seen in four participants (6%). Out of the 62 mothers, eighteen (29%) gave birth to low birth weight babies. None of the variables were found to be associated with the low birth weight.CONCLUSION: The present study did not find any significant association of low birth weight with hypovitaminosis D or maternal periodontal disease in the studied sample

Comparison of post-dural puncture headache- incidence and severity in obstetric patients after spinal anesthesia for caesarean section with 25G and 27G quincke needle

Background: The use of neuraxial anesthesia for caesarean section has dramatically increased in last 2 decades because it is easier to perform, safe to the mother and the fetus, and has a high degree of success rate. However, post-dural puncture headache is a well-known complication of spinal anesthesia. It is a common and incapacitating compliation following dura-arachnoid puncture and results in increased morbidity, prolonged hospital stay, increased cost, and patient dissatisfaction.Methods: It was a double-blinded comparative study conducted on 75 consecutive pregnant patients meeting the inclusion criteria of the study. Patient and anesthesiologist involved in collection of data were blinded to the gauge of the needle used. Standard anesthesia protocol was followed in all the patients and spinal anesthesia performed using 25G Quincke needle in 38 patients and 27G Quincke needle in 37 patients.Results: we included 75 consecutive patients in the age group 20-35 years in the study. Overall incidence of PDPH was 14.67% (11/75) in present study. 23.68% (9/38) and 5.4% (2/37) patients who received spinal anesthesia with 25G and 27G needles respectively developed PDPH. Difference was statistically insignificant.Conclusions: The incidence of PDPH was less in patients who underwent caesarean section under spinal anesthesia with 27G needle compared to that of patients in whom block was performed using 25G needles. However, there was no definite advantage of 27G Quincke needle over 25G Quincke needle as far as the incidence of PDPH is concerned